APPENDIX A- Starlet Miller

CHEMISTRY OF LIFE

 

A.  Levels of Chemical Organization

     1. Atoms

     2.  Elements, Molecules, and Compounds

 

B.  Chemical Bonding

     1.  Ionic Bonds

     2.  Covalent Bonds

 

C.  Inorganic Chemistry

     1.  Water

     2.  Acids, Bases, and Salts

 

D.  Organic Chemistry

     1.  Carbohydrates

     2. Lipids

     3. Nucleic Acids

 

 

 

Levels of Chemical Organization

 

Matter is anything that occupies space and has mass.  In the body, most chemicals are in the form of molecules.  Molecules are particles of matter that are composed of one or more smaller units called atoms.  Atoms in turn are composed of several kinds of several kinds of subatomic particles:  protons, electrons, and neutrons.  

 

Atoms

 

Atoms can be seen with these instruments; tunneling microscopes and atomic force microscopes,

Produce pictures of atoms that confirm current models of how atoms are put together.  At the core of each atom is a nucleus composed of positively charged protons and uncharged neutrons.

The number of protons in the nucleus is an atom’s atomic number.  The number of protons and neutrons combined is the atom’s atomic mass.   The number of electrons in the outer energy level of an atom determines how it behaves chemically (that is, how it may unite with other atems). This behavior is called chemical bonding.

 

 

Elements, Molecules, and Compounds

 

Substances can be classified as elements, or compounds.  Elements are pure substances, composed of only one of more than a hundred types of atoms that exist in nature.  Only four kinds of atoms (oxygen, carbon, hydrogen, and nitrogen) make up about 96% of the human body.  There are traces of about 20 other elements in the body.

Atoms usually unite with each other to form larger chemical units called molecules.  Some molecules are made of several atoms of the same element.  Compounds are substances whose

molecules have more than one element in them.  The formula for a compound contains symbols for the elements in each molecule.

 

Matter is composed of molecules, which are composed of atoms. Atoms are composed of

protons, electrons, and neutrons.  Elements are pure substances, composed of only one kind of atom.  Compounds are composed of molecules having more than one kind of atom.

 

 

 

CHEMICAL BONDING

 

Chemical bonds form to make atoms more stable.  An atom is said to be chemically stable when its outer energy level is “full” (that is, when its energy shells have the maximum number of electrons they can hold).  Outer atoms may donate or borrow electrons until the outer most energy level is full.

 

Ionic Bonds

 

One common why in which atoms make their outermost energy level full is to form ionic bonds

with other atoms. An ion is an electrically charged atom  The molecule is held together by an ionic bond. 

 

Ionic molecules usually dissolve easily in water because water molecules wedge beween the ions and force them apart.  When this happens, we say the molecules dissociate (dis-SO-see-ayt) to form free ions.  Molecules that form ions when dissolved in water are called electrolytes.

 

Covalent Bonds

 

Atoms may also fill their energy levels by sharing electrons rather than donating or receiving them.  When atoms share electrons, a covalent (ko-VAY-lent) bond forms.

 

Ionic bonding occurs when one atom donates an electron to another atom and the reslting ions attract each other.  In covalent bonding, atoms share electrons.

 

 INORGANIC CHEMISTRY 

 

In living organisms, there are two kinds or compounds: organic and inorganic.  Organic compounds are composed of molecules that contain carbon-carbon(C-C) covalent bonds or carbon-hydrogen(C-H) covalent bonds-or both kinds of bonds.  Few inorganic compounds have carbon atoms in them and none have C-C or C-H bonds.  Organic molecules are generally larger and more complex than inorganic molecules.  The human body has both kinds of compounds because both are equally important to the chemistry of life.

 

 

Water

 

   One of the compounds that is most essential to life-water-is an inorganic compound.  Water is the most abundant compound in the body, found in and around each cell.  It is the solvent in which most other compounds or solutes are dissolved.  When water is the solvent for mixture( a blend of two or more kinds of molecules),  the mixture is called an aqueous solution.  An aqueous solution containing common salt(NaCl) and other molecules forms the “internal sea” of the body.  Chemical reactions are interactions among molecules in which atoms regroup into new combinations.

   A common type of chemical reaction in the body is dehydration synthesis.  In any kind of synthesis reaction, the reactants combine to form a larger product.   In dehydration synthesis, reactants combine only after hydrogen (H) and oxygen (O) atoms are removed.   Another common reaction in the body, hydrolysis (hye-DROL-i-sis), also involves water.  In this reaction, water(hydro-) disrupts the bonds in large molecules, causing them to be broken down into smaller molecules(lysis).

   The stored energy can then be released when the chemical bonds in the molecule are later broken apart. For example, a molecule called adenosine triphosphate(ATP) breaks apart in the muscle cells to yield the energy needed for muscle contraction.

  Chemists often use a chemical equation to represent a chemical reaction.  In a chemical equation, the reactants are separated from the products by an arrow showing the “direction” of the reaction.  Reactants are separated from each other and products are separated from each other by addition signs.  The single arrow is used for equations that occur in only one direction.  The double arrow is used for reactions that happen in “both directions” at the same time.  In short, the double arrow indicates that at any instant in time both reactants and products are present in the solution at the same time.  

 

Acids, Bases, and Salts

 

   Acids and bases are compounds that profoundly affect chemical reactions in the body.  Bases or alkaline compounds, on the other hand, shift the balance in the opposite direction.  A strong acid is an acid that completely, or almost completely, dissociates to form H+ ions. A weak acid, on the other hand, dissociates very little and therefore produces few excess H+ ions in solution.

A third way to adjust the body’s pH is the use of buffers—chemicals in the blood that maintain pH.  Buffers maintain pH balance by preventing sudden changes in the H+ ion concentration.

 

Organic compounds always contain carbon (forming carbon-carbon or carbon-hydrogen bonds); few inorganic compounds even contain carbon.  Biological reactions take place in aqueous solutions.  In hydrolysis, chemical bonds are broken.  In dehydration synthesis, bonds are formed.  The pH (relative H+ concentration) of body fluids affects chemical reactions.

 

 

ORGANIC CHEMISTRY

 

   Organic compounds are much more complex than inorganic compounds.

 

Carbohydrates

 

The name carbohydrate literally means “carbon © and water (H2O),” signifying the types of atoms that form carbohydrate molecules.  The basic unit of carbohydrate molecules is called a monosaccharide(mah-no-SAK-ah-ride).  Glucose(dextrose) is an important monosaccharide in the body; cells use it as their primary source of energy.  A molecule made of two saccharide units is a double sugar or disaccharide.  The disaccharides sucrose  (table sugar) and lactose (milk sugar) are important dietary carbohydrates.  Many saccharide units joined together form polysaccharides.  Examples of polysaccharides are glycogen and starch. 

 

Lipids

 

Lipids are fats and oils.

 

   1.  Triglycerides (try-GLIS-er-ides) are lipid molecules formed by a glycerol unit joined to three fatty acids.  Triglycerides are useful in storing energy in cells for later use.

   2.   Phospholipids are similar to triglycerides but have phosphorus-containing units in them, as their name implies.  The phosphorus-containing unit in each molecule forms a “head” that attracts water.  Two fatty acid “tails” repel water.  This structure allows them to form a stable bilayer in water that forms the foundation for the cell membrane.

   3.  Cholesterol is a steroid lipid that performs several important functions in the body.  It combines with phospholipids in the cell membrane to help stabilize its bilayer structure.  The body also uses cholesterol as a starting point in making steroid hormones such as estrogen, testosterone, and cortisone.

 

Proteins

 

   Proteins are very large molecules composed of basic units called amino acids.  In addition to carbon, hydrogen, and oxygen, amino acids contain nitrogen (N). A particular sequence of amino acids is strung together and held by peptide bonds. 

   The shape of a protein molecule determines its role in body chemistry.  Structural proteins are shaped in ways that allow them to form essential structures of the body.  Collagen, a protein with a fiber shape, holds most of the body tissues together.  Keratin, another structural protein, forms a network of waterproof fibers in the outer layer of the skin.  Functional proteins  participate in chemical processed of the body.  Functional proteins include some of the hormones, growth factors, cell membrane channels and receptors, and enzymes.

   Enzymes are chemical catalysts.  This means that they help a chemical reaction occur but are not reactants or products of themselves.  Each enzyme has a shape that “fits” the specific molecules it works on, much as a key fits specific locks.  This explanation of enzyme action is sometimes called the lock-and-key-model.

 

Nucleic Acids

 

 

 

 

  The two forms of nucleic acid are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

The basic building blocks of nucleic acids are called nucleotides.  Each nucleotide consists of a phosphate unit, a sugar (ribose or deoxyribose), and a nitrogen base.  DNA nucleotide bases include adenine, thymine, guanine, and cytosine.  RNA uses the same set of bases, except for the substitution of uracil for thymine.  In the DNA molecule, nucleotides are arranged in a twisted, double strand called a double helix.   

 

Carbohydrates are composed of monosaccharide units and can be broken apart to yield energy.  Lipids are fat molecules composed mainly of glycerol and fatty acids and have many functions.  Proteins are complex strings of amino acids.  Proteins make up body structures or regulate body functions.  Nucleic acids DNA and RNA are composed of nucleotides.  The sequence of nucleotides serves as a cod for assembling proteins.

 

   

 

 Acid  any substance that, when dissolved in water, contributes to an excess of H+ ions.

 

Aqueous solution liquid mixture in which water is the solvent.

 

Atom smallest particle of a pure substance(element) that still has the chemical properties of that substance; composed of protons, electrons, and neutrons(subatomic particles).

 

Atomic mass combined total number of protons and neutrons in an atom.

 

Atomic number total number of protons in an atom’s nucleus; atoms of each element have a characteristic atomic number.

 

Base alkaline; any substance that, when dissolved in water, contributes to an excess of OH- ions.

 

Carbohydrate organic molecule composed of one or more monosaccharides.

 

Compound substance whose molecules have more than one kind of element in them.

 

Covalent bond chemical bond formed when atoms share electrons by overlapping their energy levels(electron shell).

 

Dehydration synthesis chemical reaction in which large molecules are formed by removing water from smaller molecules and joining them together.

 

Dissociation separation of ions as they dissolve in water.

 

Double helix  shape of DNA molecules; a double spiral.

 

Electrolyte compound whose molecules dissolve in water to form ions.

 

Electron negatively charged particle orbiting the nucleus of an atom.

 

Element pure substance, composed of only one type of atom.

 

Energy level limited region surrounding the nucleus of an atom at a certain distance containing electrons; also called a shell.

 

Enzyme functional protein that catalyzes chemical reactions(helps them occur more rapidly)

 

Glycogen polysaccharide consisting of a chain of glucose(monosaccharide) molecules.

 

Hydrolysis chemical reaction in which water is added to a large molecule causing it to break apart into smaller molecules.

 

Inorganic compounds compounds whose molecules generally do not contain carbon.

 

Ionic bond chemical bond formed by the positive-negative attraction between two ions.

 

Lipid organic molecule usually composed of glycerol and fatty acid units; types include triglycerides, phospholipids, and cholesterol.

 

Matter any substance that occupies space and has mass.

 

Molecule particle of matter composed of one or more smaller units called atoms.

 

Neutron electrically neutral particle within the nucleus of an atom.

 

Nucleic acid complex organic molecule composed of units called nucleotides that each include a phosphate, a five-carbon sugar, and a nitrogen base.

 

Nucleus(of an atom) central core of the atom; contains protons and neutrons.

 

Organic compounds whowe larg molecules contain carbon, which forms C-C bond and / or C-H bonds.

 

Peptide bond covalent bond linking amino acids within a protein moldcule.

 

pH unit expressing relative H+ concentration; pH value higher than 7 is basic, pH value less tha 7 is acidic, pH value equal 7 is neutral.

 

Product any substance formed as a result of a chemical reaction.

 

Protein nitrogen-containing organic compound composed of a folded strand of amino acids.

 

Protons positively charged particles within the nucleus of an atom.

 

Reactant any substance entering(and being changed by) a chemical reaction.

Solute substance that dissolves into another substance; for example, in saltwater the salt is the solute dissolved in water.

 

Solvent substance in which other substances are dissolved; for example, in saltwater the water is a solvent for salt.